1. Field of Invention
The invention relates to an improved capstan draw apparatus for periodically gripping and longitudinally drawing an elongated member such as, for example, a freshly welded, tubular sheath between a welding station and a corrugating station.
2. Description of the Prior Art
Capstan draw apparatus of the type over which the present invention improves are priorly known from, for example, U.S. Pat. No. 3,085,729. Such prior art apparatus provides for the periodic gripping and longitudinally drawing of welded tubular sheaths by the employment of a plurality of split clamps, each including a pair of clamping elements, mounted on oppositely positioned, endless driven chains. Each of the split clamps periodically engage a portion of the outer circumferential surface of the welded tubular sheath for retaining a tight circumferential grip on the smooth sheath that prevents slipping and torsional turning of the sheath.
The priorly known apparatus of this type are employed, for example, in the manufacture of thin walled, longitudinally welded, corrugated metal sheaths. Such sheaths are manufactured by the sequential steps of continuously drawing a thin metallic band through a forming station in which the band is deformed into a smooth tubular sheath; longitudinally welding the longitudinally abutting edges of such smooth sheath to each other as such smooth tubular sheath is drawn longitudinally through a welding station; and longitudinally passing the freshly welded, smooth tubular sheath through a capstan draw apparatus which periodically grips and longitudinally draws such tubular sheath in the longitudinal direction and feeds same through a corrugating station. For obtaining a uniform hermetic seal along the longitudinally welded seam, the torque imparted to the freshly welded sheath at the downstream corrugating station is isolated from the welding station by the capstan draw apparatus.
Generally, in the priorly known capstan draw apparatus, each of the plurality of rotating split clamps is positioned along and mounted directly on the oppositely positioned, endless driven chains. Consequently, each movement emitted by the driven chains, or the associated drives, is translated to each pair of clamping elements, and to the portions of the smooth tubular sheath being tightly encompassed by those pairs of clamping elements making closed engagement therewith. In such prior art apparatus it is only those rotating split clamps that are in their closed condition about the smooth tubular sheath that are positively guided as the endless chains do not in themselves provide sufficient precise guidance to the split clamps to prevent undesirable thrusts and irregularities of movement; especially, for example, in the curved portions of the path of movement of the split clamps.